What is the atomic mass of calcium?

According to Dalton’s Atomic Theory, an atom is the smallest indivisible unit of matter. However, later discoveries showed that atoms can be further divided into subatomic particles—electrons, protons, and neutrons. These particles together contribute to the total mass and properties of the atom.

The basic structure of an atom consists of a dense nucleus at the center, which contains positively charged protons and neutral neutrons. Around the nucleus, tiny negatively charged electrons move in orbitals. In a neutral atom, the number of protons equals the number of electrons.

The atomic mass of an element is essentially the total mass of protons and neutrons in its nucleus. Since the mass of electrons is negligible, it is usually ignored in the calculation. The number of protons is given by the atomic number (Z), and the sum of protons and neutrons gives the mass number (A).

For calcium (Ca):

• Atomic number (Z) = 20 → number of protons = 20.
• Number of neutrons ≈ 20.
• Mass of each proton or neutron ≈ 1 atomic mass unit (amu).

So, total atomic mass = 20 protons + 20 neutrons = 40 amu.

Hence, the atomic mass of calcium is approximately 40 u.